1. Field of the Invention
The field of the invention is inert gas bubble-actuated molten metal pumps for use in a well of a metal-melting furnace and in particular relates to an improved inert gas bubble-actuated molten metal pump incorporating a gas-diffusion grid for purposes of obviating certain disadvantages of known such pumps as well as certain other novel and advantageous characteristics, all of which will become apparent hereinafter.
2. Prior Art
The state of the art regarding the introduction of metal chips into a charge or other well of a metal-melting furnace and the conveyance of molten metal from one place to another within or out of a metal-melting furnace has been fully reviewed in the prior U.S. patents of one of us, in particular U.S. Pat. No. 5,735,935, issued Apr. 7, 1998, and the disclosure of that patent as well as of those enumerated therein is hereby incorporated by reference.
At the present state of the art, the use of an inert gas bubble-actuated molten metal pump for moving molten metal from one place to another within or out of a metalmelting furnace is now well established. The term "actuated", with reference to an inert gas bubble "actuated" molten metal pump, means that the pump is put into action by the inert gas bubbles or, synonymously, that the pump could be said to be driven, propelled, or powered by the inert gas bubbles.
Although the inert gas bubble-actuated molten metal pump of the previous U.S. Pat. No. 5,203,910 and others of one of us has met with considerable success, when such device has been employed within a metal-melting furnace to move molten metal from one place to another in the same well of the metal-melting furnace or from one well to another in a metal-melting furnace, for purposes of effecting circulation of the molten metal therein, and is a great improvement over previously-employed circulation pumps, several undesirable effects have been noted. In particular, undue spattering or splashing of molten metal at the surface of the molten metal mass above the exit port of the pump has been found objectionable per se, in addition to the fact that the splashing and spattering have caused a disruption of the protective metal oxide coating or dross which generally accumulates at the surface of the molten metal bath or pool, with the result that increased levels of oxidation, which would normally not be encountered, have occurred at the surface of the molten metal mass, and the solution to these problems has frequently required the presence of a heat-resistant and flame-resistant cover above the exit port of the bubble-actuated molten metal pump to reduce the resultant splashing and spattering at the surface of the molten metal bath or pool, as provided in the earlier U.S. Pat. No. 5,735,935 of one of us.
It would be highly desirable to eliminate the necessity of such a heat- and flame-resistant cover while at the same time avoiding the undesirable spattering or splashing of molten metal at the surface of the molten metal mass, bath, or pool above the exit port of the pump, and the present invention provides a solution to the aforesaid problems as well as providing additional advantages due to the unique details of construction of the bubble-actuated molten metal pump of the present invention.